Unit Name: Scollard Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Maastrichtian - Danian (70.6 - 61.1 ma)
Age Justification: Sternberg (1947) recorded a Lancian dinosaur fauna consisting of Tyrannosaurus rex, Triceratops albertensis, Thescelosaurus neglectus, Ankylosaurus magniventris and Leptoceratops gracilis from the lower part of the Scollard Formation. The Cretaceous-Tertiary boundary lies within the Scollard Formation, at the base of the Nevis coal seam it is marked by the extinction of dinosaurs, which coincides with a distinctive microfloral break in the region stretching from Alberta to Colorado. Dinosaur remains are unknown above the Nevis seam (Lerbekmo et al., 1979b). The Scollard Formation up to the base of the Nevis seam contains dinosaurs and microflora of Late Maastrichtian (Lancian) age. Scollard strata lying between the Nevis seam and the Paskapoo Formation contain microflora of early Paleocene (Puercan) age (Russell and Singh, 1978). The radiometric age based on potassium-argon analyses and recent magnetostratigraphic studies favor the placing of the Cretaceous-Tertiary boundary immediately below the Nevis seam (Lerbekmo et al., 1979a). The Cretaceous-Tertiary boundary lies in strata which appear to be conformable.
Originator: Irish, 1970, p. 141.
East bank of the Red Deer River, in Secs. 7 and 18, Twp. 34, Rge. 21W4M, about 8 km (5 mi) west of Scollard, Alberta. Type section incomplete, 33.7 m (111 ft) of Scollard Formation above the Nevis seam not represented. Gibson (1977) proposed a complete supplementary type section on the west bank of Red Deer River in Lsd. 7, Sec. 11, Twp. 34, Rge. 22W4M and Lsd. 3, Sec. 24, Twp. 34, Rge. 22W4M.
The Scollard Formation has a maximum thickness of 85 m (279 ft) in the Scollard area and thins to approximately 50 m (164 ft) near Ardley. It thickens considerably (up to 400 m, 1,312 ft) toward the west and can be recognized up to the eastern edge of the Alberta Foothills in the subsurface. The formation has been recognized from the Fox Creek and Swan Hills area in the north to the Delia and Rosebud area near Drumheller in the south (Green, 1972). The eastern edge of the formation follows an arc from Whitecourt in the north to the Hand Hills in the south via Wabamun Lake, Ardley and Big Valley. There appears to be a progressive bevelling of the Scotland strata from west to east and north to south.
Mainly an interbedded, interfingering sequence of argillaceous sandstone, siltstone, mudstone and shale. Thick coal seams are present in the upper part of the unit, associated with carbonaceous to coaly shale and laterally persistent bentonite beds. Fine grained, quartzose, bentonitic, often calcareous, light grey to buff sandstone units are interbedded with light greenish grey, bentonitic, sandy to silty mudstone, argillaceous siltstone and dark purplish grey bentonitic, sandy to silty claystone and shale. Medium to micro-scale planar and festoon cross-bedding are common in the calcite-cemented sandstone. The unit as a whole shows rapid lateral and vertical lithofacies changes. The following coal seams are present in the Scollard Formation. Nevis Coal Seam: Allan and Sanderson (1945, p. 48, 57) named this seam the Nevis seam No. 13 in the type area of the Scollard Formation, where it occurs 41 to 46 m (135 to 151 ft) above the base of the formation. It is up to 0.4 m (1.3 ft) thick and consists of interlaminated carbonaceous shale, thin lenses of vitreous coal and a laterally persistent bentonite bed. The stratigraphic level of the Nevis seam is extremely variable regionally. In the subsurface of the Pigeon Lake area (Twp. 48, Rge. 27W4M) it lies only 15.5 m (51 ft) above the base of the Scollard Formation. The seam is best developed in the subsurface near Red Deer, Ponoka, Pigeon Lake and Drayton Valley, where it is 1.5 to 3.5 m (5 to 12 ft) thick (Hotter et al., 1975, Fig. 15a). Ardley Coal Seam: Allan and Sanderson (1945, pp. 48, 57) designated this seam the Ardley seam No. 14 "in the vicinity of Ardley, and outcrops along the slopes of the Red Deer Valley, from Ardley in Twp. 38, southward to Twp. 32." In the Scollard area it lies 57.6 to 64.6 m (189 to 212 ft) above the base of the Scollard Formation and is 2.2 to 3.2 m (7 to 11 ft) thick. It consists of interbedded coal up to 1.8 m (6 ft) thick, carbonaceous shale and laterally persistent bentonite beds. The interval between the Ardley seam and the base of the Scollard Formation thins rapidly toward the north, so that the seam lies 34.6 to 44 m (114 to 144 ft) above the base of the formation in the subsurface of the Ardley area (40-26W4; 39-24W4) and only 27 m (89 ft) in the Pigeon Lake area (Twp. 48, Rge. 27W4M). The Ardley seam is the most prominently developed coal unit in the south-central and west-central Alberta Plains. It is 5 to 7 m (16 to 23 ft) thick in the subsurface south of Red Deer, Lacombe and west of Bearhills Lake and reaches a maximum thickness of 9 to 13 m (30 to 43 ft.) in the Wabamun Lake area (Holter et al., 1975, Fig. 15a). The Ardley seam has been referred to as the "Big Seam" on the North Saskatchewan River west of Edmonton, as the "Pembina seam" at Evansburg and as the "Wabamun seam" near Lake Wabamun. An "Ardley-equivalent coal zone" (1.5 to 4.5 m thick) exists farther north around Swan Hills, Fox Creek and south of Grande Prairie (Kramers and Mellon, 1972; Campbell, 1972). "Upper Ardley" Coal Seam: Holter et al. (1975) described a series of coal seams occurring 15 to 46 m (49 to 151 ft) above the Ardley coal seam from the subsurface of southcentral Alberta. The seams consist of interbedded coal, carbonaceous shale and minor bentonite. High quality coal is rare and thicknesses exceed 1.5 m (5 ft) only in a small area between Warburg and Pigeon Lake (Holter et al., 1975, Fig. 15b).
The Scollard Formation appears to be conformable with the underlying mauve to purplish black, bentonitic shale of the Battle Creek Formation in most of the area. The contact is sharp and abrupt. According to Irish (1970, p. 139) the Battle Formation has been partly or wholly removed by erosion at some localities (Twp. 26, Rge. 21W4M; Twp. 22, Rge. 23W4M) in southern Alberta, signifying a definite unconformity between the two units. The upper contact of the Scollard Formation with the massive, cliff forming, orange brown sandstone of the Paskapoo Formation is sharp and usually marked by some channelling and erosion. The hiatus at this level is too small in the Red Deer River area to substantiate a major unconformity postulated by Allan and Sanderson (1945). However, the possibility exists of an unconformity in the south, between the Bow and Oldman rivers, where a Paskapoo-type sandstone of uncertain age rests on the Battle Formation or older strata (Tozer, 1956, p. 30; Irish, 1970, p. 142). The Scollard Formation is correlative with the uppermost part of the Wapiti Group, above the Kneehills Tuff marker, in northwestern and central Alberta, and the Coalspur Formation of the central Alberta Foothills. It is correlative with all or most of the Willow Creek Formation in the Porcupine Hills area of southwestern Alberta, and with the Frenchman and Ravenscrag (lower part) formations in the Cypress Hills area of southwestern Saskatchewan. It is correlative also with the Hell Creek, Lance and Fort Union (lower part) formations of Montana and Wyoming.
First named as "Upper Edmonton member" by Allan and Sanderson (1945) and as "Member E" by Ower (1960). Later Irish (1970, p. 141) designated as the Scollard Member all the "strata between the Battle Formation and the uppermost coal seam of the coaly zone (so called Ardley coal zone)." Gibson (1977) added the younger strata lying between the Ardley seam and the Paskapoo Formation to the unit and raised it to formational status.
Allan and Sanderson, 1945; Campbell, 1972; Gibson, 1977; Green, 1972; Holter et al., 1975; Irish, 1970; Kramers and Mellon, 1972; Lerbekmo et al.. 1979a; Lerbekmo et al., 1979b; Ower, 1960; Russell and Singh, 1978; Sternberg, 1947; Tozer, 1956.
Irish, E.J.W., 1970. The Edmonton Group of south-central Alberta; Canadian Society of Petroleum Geologists (CSPG), Bulletin of Canadian Petroleum Geology, vol. 18, no. 2 (June), pp. 125-155.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: C. Singh
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 28 May 2008